AAS 206th Meeting, 29 May - 2 June 2005
Session 38 Interstellar Medium, H II Regions and Molecular Clouds
Poster, Wednesday, 10:00am-7:00pm, Thursday, 9:20am-2:00pm, June 1, 2005, Ballroom A

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[38.01] The relationship between the D/H, D/O, and O/H ratios and the mean sightline density.

C. M. Oliveira, H. W. Moos (Johns Hopkins University)

Deuterium, produced during primordial nucleosynthesis and then destroyed by astration, is a key element for investigating cosmology. The present-epoch deuterium abundance, D/H, measured in the interstellar medium, is then a lower limit to the primordial abundance of deuterium, and an important constraint of Galactic chemical evolution models.

Recent results have shown that the abundance of deuterium in the Local Bubble (LB, d < 100 pc) is constant, (D/H)LB ~ 15.0 ppm. However, beyond 100 pc, measurements of D/H along more than 10 sightlines show a range of D/H values that are in significant disagreement with the LB value and inconsistent with the predictions of current Galactic evolution models. Large variations of D/H over distance scales of ~ 100 pc make it hard to understand these variations in terms of variable astration or variable infall of primordial gas.

Depletion of deuterium onto dust grains has been proposed as a possible mechanism to explain the observed D/H variations. Several studies have shown that the strengths of the depletions of elements such as Fe and Si, for instance, scale in proportion to the mean sightline density. This depletion effect has been commonly interpreted as the result of a fraction of these elements being locked up in dust grains. In this work we investigate the variations of the D/H ratio by exploring the relationship between the D/H, D/O, and O/H ratios measured along multiple sightlines with the mean sightline density.

The author(s) of this abstract have provided an email address for comments about the abstract: oliveira@pha.jhu.edu

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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.